Mr Perepilichnyy, 44, had been helping Bill Browder’s Hermitage Capital Investment to expose a 230 million dollar money-laundering operation, the court has heard.

A month before his death, he had fought off a legal challenge by a debt recovery firm allegedly led by the prime suspect in the Alexander Litvinenko poison case.

Coroner Nicholas Hilliard QC is examining if Mr Perepilichnyy died of natural causes or was murdered.

Ms Medynska, who works in fashion, appeared at the Old Bailey by video link from Paris.

She told how she met Mr Perepilichnyy through a dating agency and he paid for their dates, staying in smart hotels in Kiev, Nice and Paris over eight months.

The inquest heard he changed hotels and used a false name, keeping the relationship “secret”.

Describing their date on November 8 2012 in Paris, the former model said: “When I met him in hotel he was smile, he was calm, relaxed but when we went out at lunchtime he was a little bit nervous.

“I think he was nervous about his work or business. I did not ask him questions about if something happened, I just want to have relaxing time with him. I talked him about subject to make him relaxed because he was very stressed when I met him.”

At lunch in a bistro, she said his hands were shaking so much he spilt his red wine.

She said they went back to the hotel before having a late dinner at a restaurant where he had soup and more red wine.

The next day, he spoke on his phone and was on “another planet”.

She said: “I think maybe he was a businessman. He have his own secrets but I never asked him.”

Peter Skelton, counsel for the coroner, asked: “Did he seem stressed or more relaxed?”

Ms Medynska replied: “Sometimes I have feeling he is somewhere else because he is not very communicate with me.”

She said he took her shopping for shoes because she was not in a “nice mood”.

She said: “He was on another planet. I was little bit upset and he said let’s make shopping together. When I was shopping shoes he was not looking at me. He was watching his phone. I was upset because he gave me no attention and I was not in very good mood.”

Mr Skelton asked if he might have been distracted by work.

She said: “Maybe he missed some mails. I respect him as a businessman. I understood he has a job to do even if he is spending time with a woman in Paris.”

On November 9 they went out to the Buddha Bar for dinner but he sent back his tempura prawns because it was “not nice”, she said.

The restaurant specialised in Chinese and Japanese food and he ate either sushi or tempura, the inquest heard.

Ms Medynska said: “He said he did not like the taste. He was very irritated. He was very mad about the quality of the food.”

As they walked back to the hotel, he told her he felt “better in the fresh air”, but when they got back in their hotel suite, she said he vomited three times in the bathroom, the inquest heard.

She said: “I think maybe he vomited because it was not good food in the restaurant. I did not knock on the door because I did not want to make him feel uncomfortable.”

The witness said he “looked clean” when he came out of the bathroom and by the morning he was in “good shape”.

In the morning of November 10, she said he was “looking very nice, good mood, smile”.

They ate a “classic French breakfast” of eggs and hot chocolate before going to the airport together, for Mr Perepilichnyy to return to London and Ms Medynska to Ukraine.

She said: “He told me he wanted to see me. He said he want to meet in December in Switzerland.”

Later the same day, Mr Perepilichnyy died near his home.

The witness said she received a call from a British number and was told Mr Perepilichnyy had been in a car accident.

She said: “I was very shocked and afraid about this news. I thought it was like a bad joke happened to me.”

She told the inquest she found out about his death from the internet on New Year’s Eve 2012.

The witness said she was “scared because I know nothing about this man”, and had no idea he was married with children.

Later, she said she received a threatening message from Mr Perepilichnyy’s email to say she would “die soon” from Aids.

Later, the court heard that Russian prime minister Dmitry Medvedev had been in Paris between November10 and 13, but the witness did not know it at the time.

During their shopping trip, Mr Perepilichnyy bought his girlfriend a Prada bag and pair of Louis Vuitton shoes.

Two days after his death, Ms Medynska said she received two calls from people who purported to be from a hospital where Mr Perepilichnyy was taken after a “car accident”.

They told her his phone was broken but text messages appeared to show she was the last person to see him.

Mr Browder sat in court for the second day of the resumed inquest which began last summer.